Cognitive Impairment Across Kidney Replacement Therapies: A Montreal Cognitive Assessment-Based Comparative Study

Objectives Cognitive impairment is a prevalent, often underdiagnosed complication of end-stage kidney disease. This study compared cognitive function among patients receiving hemodialysis or peritoneal dialysis and kidney transplant recipients with that of healthy controls using the Montreal Cognitive Assessment, a validated screening tool for global cognitive function. The primary outcome was the total Montreal Cognitive Assessment score, with cognitive impairment defined as a score <26. Methods A total of 147 participants were enrolled: 32 peritoneal dialysis patients, 31 hemodialysis patients, 42 kidney transplant recipients, and 42 healthy controls. Cognitive performance was assessed using Montreal Cognitive Assessment total and domain scores. The Montreal Cognitive Assessment was administered to hemodialysis patients before their scheduled dialysis session, whereas peritoneal dialysis patients and kidney transplant recipients were assessed during routine outpatient follow-up visits. Multivariable linear and logistic regression models identified independent predictors of cognitive performance and risk factors for impairment (score <26). Results Total cognitive scores were significantly lower in all patient groups than in controls; the hemodialysis group exhibited the lowest performance (20.29 ± 5.49 vs. 24.52 ± 2.98, p < 0.001). The prevalence of cognitive impairment (Montreal Cognitive Assessment score <26) was 37.5% in the peritoneal dialysis group, 48.4% in the hemodialysis group, 38.1% in the kidney transplantation group, and 15.0% among healthy controls. Hemodialysis patients performed significantly worse than kidney transplant recipients in the attention domain (p = 0.015). In the fully adjusted multivariable model, age (β = -0.120, p < 0.001) and education level (p < 0.001) were the only independent predictors of cognitive scores. Although hemodialysis patients showed a trend toward a higher prevalence of impairment, treatment modality was not an independent risk factor after adjustment for demographic factors (p = 0.123). Higher education was strongly protective, reducing the risk of impairment by 93.9% (adjusted odds ratio: 0.061, p < 0.001). Conclusion Cognitive impairment is common among patients with end-stage kidney disease and is likely multifactorial, with contributing factors including vascular disease, chronic inflammation, anemia, and the accumulation of uremic toxins. Although hemodialysis patients demonstrated lower cognitive performance and a higher prevalence of impairment, age and education, rather than treatment modality, were the principal independent determinants of cognitive outcomes.